This invention relates to the improvement of performance of an outboard engine.
A two-cycle outboard engine has heretofore mainly been used on a boat for leisure-time amusement and fishing because a two-cycle engine is small and light weight and yet capable of developing great power.
However, the engine also has a problem of causing water pollution because of the mixed fuel it uses. It also gives an unpleasant feeling to people because it exhausts a lot of hydrocarbon (hereinafter referred to as HC). Furthermore the engine is sometimes difficult to start as the plug is susceptible to damage.
An object of the present invention is to provide a four-cycle outboard engine equipped with a supercharger in order to solve the problems of a two-cycle engine and yet to maintain great power.
Another object is to provide a multi-cylinder outboard engine which has a good mixture-distributing condition for each cylinder.
A further object is to provide an outboard engine which can cool the air or mixture in the intake manifold supplied by the supercharger, connecting the supercharger with each port of the cylinder heads.
A further object is to provide an outboard engine which can prevent an engine burning out by cooling the lubricating oil in the oil pan.
A further object is to provide an outboard engine that has a lubricating oil-supplying hole through which the oil can be supplied on board and the inspection of the condition of the oil can be precisely done on board.
A further object is to provide an outboard engine which has a thrust metal with somewhat free-setting location on the crankshaft and with rotary stopper means which need not a lot of machining processes.